Contact lists are used to store contact information for individuals and businesses. Users typically add a new contact to their contact list when they are introduced to another person or meet the other person in some social context. In many cases, the information for a contact in the contact list is incomplete. For example, a contact may include just a person's first name and telephone number, but lack the person's last name, email address, business address, or fax number.
Incomplete information can be used for some purposes but may not be useful for other purposes. For example, if the contact information for a person includes only an email address, the user does not have the phone number to call that person or the address to send a letter by mail. Users who own multiple client devices, for example, smartphone, tablet, laptop, etc., may store inconsistent information in contact lists across different client devices, such as different contacts in contact lists, or the same contact with different information. To summarize, contact information stored in client devices of a user may have missing information and/or inconsistent information.